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[From  the  Journal  0/  Physiology.      Vol.  XIII.  Nos.  3  l-  4,  189 2. J 


M4^ 


ON  THE  RESPIRATORY  CHANGES  OF  THE  INTRA- 
THORACIC PRESSURE,  MEASURED  IN  THE  ME- 
DIASTINUM   POSTERIOR.     By    Dr    S.    J.   MELTZER, 

New  Yorh     (Plates  VIII.  A  and  VIII.  B.). 

From  the  Physiological  Laboratory  of  the  College  of  Physicians  and 
Surgeons  of  the  City  of  Neiv  York. 

It  is  a  well-known  pathological  fact  that  tuberculosis  shows  a  decided 
preference  for  the  apices  of  the  lungs.  This  was  often  explained  by  the 
assumption  that  the  apex  is  not  participating  fully  in  the  respiratory 
movements,  and  that  the  diminished  ventilation  of  the  said  locality  is 
the  cause  of  its  predisposition  for  the  disease.  But  as  it  is  now  an 
established  teaching  that  an  invasion  of  tubercle  bacilli  in  the  lungs  is 
at  the  bottom  of  the  disease,  we  should  rather  expect,  that  if  the  apex 
breathes  less,  the  bacilli  will  have  less  chances  of  getting  in  there,  and 
in  consequence  this  part  of  the  lungs,  instead  of  being  predisposed  for 
the  disease,  should  rather  show  a  certain  immunity  against  it.  To 
overcome  this  obstacle  A.  Hanau'  undertook  to  modify  the  hypothesis, 
by  assuming  that  the  expiration  is  indeed  less,  whereas  the  inspira- 
tion is  rather  better  in  the  apex  than  in  the  other  parts  of  the  lungs, 
therefore  all  corpuscular  elements  of  microscopical  dimensions,  like  the 
bacilli,  dust  etc.,  have  a  greater  chance  to  get  in  the  alveoli  of  the  apex, 
while  their  chances  to  get  out  of  these  by  the  expiration  is  reduced. 
This  hypothesis  would  cover  indeed  the  pathological  phenomenon 
satisfactorily.  Unfortunately  for  this  hypothesis,  the  normal  breathing 
also  has  to  be  taken  in  consideration.  What  would  be  the  fate  of  the 
apex,  if  the  inspiration  should  considerably  overbalance  the  expiration, 
if  more  air  should  get  into  the  alveoli  than  could  come  out  ? 

Instead  of  speculating  upon  the  normal  status  from   pathological 
facts,  we  should  endeavour  firstly  to  study  the  normal  process  in  due 

'  A.  Hanau.     ZeiUchrift  fur  klinisclte  Medizin.    Bd.  xii. 


INTRATHORACIC  PRESSURE.  219 

manner  by  physiological  methods.  It  is  a  matter  pertaining  to  physio- 
logy to  decide,  if  iu  normal  breathing  all  parts  of  the  lungs  are  equally 
sharing  in  the  respiratory  act.  But  there,  in  physiology,  the  point  in 
question  is  even  not  raised  to  the  rank  of  a  problem.  I  failed  to  find  in 
physiological  literature,  even  a  serious  discussion  of  our  question.  In 
the  face  of  the  decided  predilections,  however,  shown  by  certain  parts  of 
the  lungs  to  certain  pathological  processes  (Tuberculosis,  Pneumo- 
coniosis, Emphysema,  etc.)  physiology  cannot  afford  to  ignore  this 
problem,  or  to  solve  it  with  mere  theoretical  speculations  like  the 
application  of  the  physical  laws  of  elasticity  on  the  lungs,  i.e.  that  an 
elastic  band  shows  equal  distensions  in  all  its  parts \ 

As  it  is  very  difficult  to  find  an  exact  method  to  ascertain  directly 
the  degree  of  the  distensions  of  the  apex,  as  compared  with  those  of  the 
other  parts  of  the  lungs  during  normal  breathing,  I  turned  my  attention 
firstly  to  a  phenomenon  steadily  accompanying  those  distensions ;  it  is 
the  change  of  the  intrathoracic  pressure  coinciding  with  the  inspira- 
tion and  expiration.  There  are  at  present  three  different  methods  for 
determining  the  intrathoracic  pressure.  The  first,  and  oldest  method, 
and  as  it  was  shown  by  Heynsius^  probably  the  most  reliable  one,  is 
that  which  was  introduced  by  Bonders^  and  Hutchinson'':  to  connect 
a  manometer  with  the  trachea  of  a  dead  animal  and  to  open  both  the 
pleurae.  We  could  of  course  not  employ  this  method,  which  informs  us 
only  of  the  sum  of  negative  pressure  prevailing  in  the  whole  pleural 
cavity  while  the  respiratory  muscles  are  entirely  at  rest.  Another 
method  which  seemed  to  be  more  appropriate  for  our  purpose,  is  to 
connect  a  manometer  carefully  direct  with  the  pleural  cavity  as  it  was 
practised  by  Fredericq^,  Bernstein",  Weil'  and  others.  For  my 
purpose,  I  should  have  to  connect  two  manometers  at  different  levels 
of  the  chest  wall  of  a  living  animal.  I  have  tried  it;  but  soon  convinced 
myself  that,  just  as  Heynsius  supposed  it  to  be,  we  never  get  by  this 
method  the  exact  intrathoracic  pressure  as  it  prevails  in  a  normal 
condition.  By  removing  carefully  all  the  muscular  tissue  in  one  or  two 
iiiterco.stal  spaces,  I  could  observe  through  intact  pleura  the  motions  of 

'  See  I.  Rosentlial.     Hermnnna  Iltnidlnich  d.  Phi/iiiohgie.     Bd.  iv.  2  Theil,  S.  180. 

*  A.  HcynHius.     "  Uebor  die  grosse  der  ncKativen  Drucke  im  Tliorax  beim  rubigem 
Atlimen."     Pfiiinttr's  Anhiv  fUr  Phijsiolwjie.    Bd.  xxix.  1882. 

^  ZeiUchrift  fiir  rat.  Medicin.  Bd.  in. 

*  Hutchinson  in  Todd's  Encijclopaedia  nf  Anatomy  and  Pliijsiologij. 

*  Fredericq.     Arcliiv  de  Bioln(jie.    1882. 

*  Bernstein,  Jul.     PjHir/er's  Aicliiv.     Bd.  xxviii. 
'  Weil.     Archiv  fiir  klininrlte  Medicin.    Bd.  xxviii. 


220  S.   J.   MELTZER. 

the  lungs,  and  thus  could  control  the  state  of  the  lungs.  In  this  way 
I  found  out  that  every  attempt  of  mine  to  connect  the  pleural  cavity 
with  a  manometer  was  met  with  some  degree  of  retraction  of  the  lung, 
which  if  not  for  the  direct  observation,  does  not  manifest  itself  otherwise. 

The  third  method,  which  was  introduced  by  Luciani^  and  I. 
RosenthaP,  and  which  seemed  to  be  indeed  the  most  appropriate 
for  my  purpose,  is  to  measure  the  intrathoracic  pressure  in  the  thora- 
cic part  of  the  oesophagus.  This  can  be  done  in  a  living  animal  with- 
out further  preparation,  by  introducing  a  tube  (katheter)  through  the 
mouth  into  the  oesophagus.  The  tube  has  to  be  of  some  thickness  to  fill 
out  the  lumen  of  the  oesophagus,  but  then  on  one  hand  it  interferes  with 
the  breathing,  and  on  the  other  hand  it  makes  the  oesophagus  con- 
tract, which  of  course  alters  the  pressure  within  it.  I  therefore  made 
an  incision  in  the  oesophagus,  pushed  in  through  the  opening  a  small 
katheter,  and  tied  the  oesophagus  and  katheter  with  a  rubber  thread,  so 
as  to  have  the  oesophagus  air-tight  around  the  katheter  and  at  the  same 
time  to  be  still  able  to  push  the  katheter  up  and  down  within  the 
oesophagus.  This  was  done  in  three  rabbits.  I  shall  briefly  state  that 
I  could  not  discover  any  constant  difference  in  the  negative  pressure 
between  the  upper  and  lower  parts  of  the  oesophagus.  At  the  same 
time  these  few  experiments  were  sufficient  to  convince  me  of  the 
correctness  of  the  statement  made  by  Heynsius^,  that  the  pressure 
within  the  oesophagus  does  not  correspond  to  the  exact  pressure  of 
the  pleural  cavity,  the  pressure  in  the  oesophagus  being,  as  it  was 
proven  by  Heynsius,  not  only  considerably  less,  but  ajso  inconstant, 
and  consequently  unappropriate  to  throw  light  on  our  subject.  The 
thickness  of  the  oesophagus  wall,  the  muscular  tissue  and  its  irregular 
contraction  provoked  by  the  presence  of  a  foreign  body  (katheter) 
are  probably  the  cause,  as  Heynsius  points  out,  of  the  reduction 
of  the  pressure  and  its  irregularity.  I  may  add,  that  every  act  of 
deglutition,  which  occurs  quite  often  on  account  of  the  moving  of 
the  katheter,  changes  the  pressure  within  the  oesophagus  considerably, 
the  change  lasting  for  some  time. 

Looking  out  for  a  new  method  by  which  I  could  compare  the 
intrathoracic  pressure  at  different  levels  of  the  thorax,  my  attention 
was  turned  to  the  mediastinum  posterior,  just  by  the  last-mentioned 
experiments  made  on  the  oesophagus.     The  only  objectionable  features 

^  Luciani.     Archivi per  le  scienze  medichi.   1878. 
^  Bosenthal  I.     du  Bois  lieymond's  Archiv.    1882. 
^  loc.  cit. 


INTRATHORACIC  PRESSURE.  221 

of  this  locality  were,  as  we  just  pointed  out,  the  effects  resulting  from 
the  thickness  of  the  oesophagus  wall  and  its  muscular  tissue.  Now  if 
we  could  determine  the  pressure  alongside  of  the  ossophagus,  but  outside 
of  it,  i.e.  in  the  mediastinum  posterior,  there  will  be,  we  should  expect, 
no  more  objections  to  the  conclusions  drawn  from  the  results  obtained 
in  this  locality  as  to  the  real  state  of  the  pressure  in  the  pleural  cavity, 
as  the  thin  layer  of  tissue  separating  the  mediastinum  from  the  pleural 
cavity  could  not  amount  to  much.  The  same  consideration  gave  me  at 
the  same  time  an  idea  how  to  gain  access  to  the  mediastinum :  along- 
side the  oesophagus  which  is  surrounded  on  its  entire  way  by  loose 
connective  tissue ;  this  is  a  convenient  path,  unfortunately  very  often 
preferred  by  the  pus  of  retropharyngeal  abscesses — why  should  we  meet 
with  ditficulty  by  pushing  a  katheter  down  the  same  way  ? 

It  is  this  method  and  some  results  I  obtained  by  it  I  intend  to 
report  here. 

With  a  single  exception  my  experiments  were  made  on  rabbits,  the 
results  therefore  are  so  far  restricted  to  this  class  of  animals  only.  The 
single  experiment  I  made  on  a  young  dog,  however,  convinced  me  that 
the  method  will  be  practicable  in  these  animals  also,  and  that  the 
results  will  probably  not  differ  materially.  All  the  animals  have  been 
narcotized  with  chloral.  This  offers  the  advantage  that  the  breathing 
continues  regularly  and  is  less  frequent.  I  wish  to  emphasize,  however, 
that  the  introduction  of  the  katheter  into  the  mediastinum  does  not 
alter  the  respiration  even  in  the  absence  of  narcosis.  The  procedure 
is  simple,  though  I  lost  many  an  experiment  before  settling  it. 

The  rabbit  being  placed  on  its  back,  the  skin  of  the  neck  was  cut 
lengthwise  on  the  larynx,  and  opposite  the  crico-thyroideal  ligament, 
a  path  was  bored  with  a  blunt  instrument  on  the  left  sterno-hyoideal 
muscle  to  its  outer  margin,  and  here  a  narrow  entrance  was  bored 
behind  the  lower  part  of  the  pharynx.  Into  this  opening  a  katheter  was 
introduced  and  pushed  downward  parallel  and  behind  the  oesophagus. 
Three  centimeters,  counted  from  the  mentioned  ligament,  may  be  pushed 
down  at  once,  as  at  this  distance  the  blind  end  of  the  katheter  is  even 
in  small  rabbits  still  above  the  aperture  of  the  chest.  All  further 
pushing  has  to  be  done  carefully,  groping,  and  in  small  distances,  about 
five  millimeters  each.  The  direction  should  be  towards  the  middle  of 
the  aperture,  the  katheter  can  be  felt  through  the  skin  behind  the 
trachea,  and  it  is  advisable,  while  pushing  the  katheter  with  one  hand, 
to  control  the  lower  end  with  two  fingers  just  above  the  aperture  in 
order  to  keep  in  the  right  direction,  and  at  the  same  time  to  press  the 


222  S.   J.   MELTZER. 

end  a  little  backwai'd  to  facilitate  its  entrance  into  the  mediastinum 
posterior,  as  there  is  a  tendency  for  the  lower  end  of  the  katheter,  while 
entering  the  thorax,  to  stumble  against  the  incisura  sterni,  on  account 
of  the  convexity  of  the  spinal  column  in  this  region.  In  fact,  the 
entrance  of  the  katheter  into  the  chest  is  the  main  difficulty,  in  older 
animals  more  so  than  in  younger  ones,  not  only  for  the  reason  of  the 
greater  curvature  of  the  spinal  column,  but  also  on  account  of  the 
greater  firmness  of  the  connective  tissue  obstructing  the  entrance  of 
the  chest.  Drawing  back  the  katheter  should  be  avoided,  as  this  might, 
as  it  would  be  seen  later,  destroy  the  entire  experiment.  Elevating 
the  outer  end  of  the  katheter,  which  would  facilitate  its  entrance 
into  the  chest,  should  also  be  avoided,  as  this  makes  the  channel  leading 
to  the  mediastinum  too  wide  and  facilitates  the  entrance  of  air  beside 
the  katheter.  This  latter  should  be  of  a  very  small  calibre ;  with  an 
English  katheter  No,  5  (lumen  about  two  millimeters)  I  never  found 
an  insurmountable  obstacle  in  pushing  it  in.  The  katheter  is  blind  at 
the  end,  and  has  one  side  opening  near  it ;  I  made  another  opening 
opposite  the  first  one.  The  lower  half  of  the  katheter  was  divided 
by  marks  (small  cuts)  in  5  millimeters  distances.  The  amount  of 
pressure  in  the  mediastinum  was  ascertained  by  connecting  the 
katheter  either  with  a  water  manometer,  or  with  a  Marey's  tambour. 
In  the  latter  case  the  respiratory  undulations  of  the  mediastinum 
have  been  recorded  graphically  in  the  usual  manner,  on  a  revolving 
cylinder  covered  with  smoked  paper.  Below  the  lever  writing  these 
undulations  another  lever  was  placed  marking  the  time  in  seconds.  The 
distance  between  the  two  lines  traced  upon  the  graphic  table  before 
connecting  the  tambour  with  the  mediastinum,  represents  the  atmo- 
spheric pressure;  a  smaller  distance  means  a  negative,  a  greater  distance 
positive  pressure.  The  manometer,  or  the  Marey's  tambour,  was  con- 
nected with  the  katheter  by  means  of  rubber  tubing,  which  had  to  be 
long  enough  to  facilitate  the  handling  of  the  katheter.  The  connection 
was  made  of  course  before  the  katheter  was  introduced  behind  the 
pharynx;  there  was  no  clamp  or  stopcock  between  the  katheter  and  the 
manometer.  Before  the  katheter  entered  into  the  chest,  there  was  usually 
no  difference  in  the  level  of  the  water  in  the  two  sides  of  the  mano- 
meter, but  if  there  was  any  difference,  it  was  of  course  taken  into  account. 
The  pushing  was  done,  as  stated,  in  5  millimeters  distances.  At  each  step 
notes  of  the  pressure  were  taken  as  it  presented  itself  during  the  inspi- 
ration and  expiration,  the  time  of  observation  being  from  5 — 6  minutes. 
There  was  hardly  any  necessity  for  taking  the  mean  of  a  number  of  obser- 


INTRATHORACIC  PRESSURE.  223 

vations,  as  at  each  step  hardly  a  difference  of  auy  account  between 
the  inspirations  could  be  noticed.  At  each  step,  besides  the  pressure, 
the  number  of  respirations  was  counted.  After  finishing  the  experi- 
ment, and  killing  the  rabbit,  I  made  in  many  experiments  an  autopsy 
to  ascertain  the  side  where  the  katheter  found  its  way,  and  some  of  the 
localities  in  the  mediastinum  corresponding  to  the  different  distances 
from  the  crico-thyroideal  ligaments  as  they  were  furnished  by  the 
preceding  experiment. 

Passing  over  to  the  results  obtained  by  this  method,  I  shall  say  in 
the  beginning,  that  we  have  to  distinguish  between  the  first  introduction 
on  the  one  hand,  and  the  retraction  and  all  the  following  reintroductions 
on  the  other  hand.  While  in  the  latter  cases  there  were  hardly  any 
constant  differences  among  the  several  parts  of  the  mediastinum,  the 
pressure  being  about  the  same  in  the  entire  length  of  it,  we  found  in  all 
the  first  introductions  of  the  katheter,  the  pressure  differing  remarkably 
according  to  the  locality  of  the  mediastinum,  which  latter  may  therefore 
be  divided  into  five  sections.  The  first  section  comprises  the  part  of  the 
mediastinum  within  the  first  ribs  and  first  intercostal  spaces ;  there 
in  most  of  the  cases,  during  the  inspiration,  either  we  found  no  change 
in  the  pressure  at  all,  or  the  change  was  so  small  that  it  could  not  be 
measured.  In  a  few  cases  the  inspiratory  difference  in  the  pressure 
.amounted  to  from  2 — 3  millimeters  of  water,  and  only  in  two  cases  the 
change  came  up  to  6  or  8  millimeters  of  water.  Nearly  the  same  can  be 
stated  of  the  condition  of  the  pressure  during  the  expiration — "Bonders' 
negative  pressure."  In  most  cases  there  was  no  negative  pressure,  at 
Iea.st  it  was  hardly  perceptible,  but  in  a  few  cases  the  negative  pressure 
was  measurable,  and  reached  in  a  couple  of  experiments  from  14  to  16 
millimeters  !  On  the  other  hand,  there  were  a  few  other  cases  showing 
at  the  expiration  a  positive  pressure  of  from  2  to  3  millimeters.  Then  a 
section  of  2 — 4  centimeters  length  follows,  where  the  inspiratory  changes 
are  generally  larger  than  in  the  first  section.  In  many  cases  a  gradual 
increa.se  in  the  amount  of  the  inspiratory  change  of  the  pressure  could 
be  observed  taking  place  downward,  the  highest  amount  observed 
being  IG  millimeters ;  but  this  was  by  no  means  the  rule ;  there 
have  been  cases  where  the  amount  of  the  change  in  a  deeper  place 
was  even  .smaller  than  in  a  higher  one.  The  expiratory  pressure  in 
this  section  is  in  nearly  all  of  the  cases  of  a  negative  character,  the 
amount  being  generally  also  larger  than  in  the  former  section,  but 
it  exceeded  only  in  exceptional  cases  the  pressure  of  10  millimeters 
water  ;  a  gradual  increase  was  here  the  exception. 

PH.  XIII.  15 


224  ;Sf.   /.   MELTZER. 

In  80  7o  of  all  the  cases,  a  section  of  from  1 — 2  centimeters  length 
now  followed,  wherein  again  no  movements  at  all  or  very  small  move- 
ments could  be  observed  in  the  manometer  during  the  inspirations, 
though  sometimes  the  heart-beat  could  be  recognized.  The  level  of  the 
water  on  both  sides  of  the  manometer  has  been,  while  in  this  section, 
either  equal  or  there  has  been  a  very  small  difference  in  favour  of  the 
negative  pressure  ;  in  other  words,  while  the  inspiration  did  not  show 
any  influence  there  has  been  little  or  none  at  all  of  Bonders'  negative 
pressure. 

The  section  which  follows  now  comprises  nearly  the  whole  remainder 
of  the  mediastinum.  In  all  the  animals  experimented  upon  a  remark- 
able turn  took  place  at  this  section.  The  inspiratory  change  of  the 
pressure  became  considerably  larger,  and  continued  to  be  the  same  with 
comparatively  small  variations  in  the  whole  section.  The  exact  amount 
of  the  inspiratory  change  varied  considerably  in  different  animals,  as 
much  as  from  15  to  60  millimeters  of  water.  There  seemed  to  be  a 
number  of  points  causing  the  difference  in  the  amount  of  the  undu- 
lations, for  instance,  the  size  and  age  of  the  rabbit,  the  number  of 
respirations  per  minute,  and  other  points,  which  I  do  not  care  to  enume- 
rate, as  I  did  not,  for  the  present,  make  a  close  study  of  this  question. 
The  negative  pressure  in  the  expiratory  state  showed  in  this  section 
in  general  the  same  sudden  change  in  the  increase,  but  the  proportion 
of  the  increase  was  somewhat  smaller,  and  there  were  a  number  of 
exceptions ;  as  for  instance,  either  without  any,  or  with  only  a  small 
increase,  or  again  the  increase  having  already  occurred  a  little  above 
this  section.  Below  this  section  it  occurred  in  some  animals  that  the 
inspiratory  change  was  again  reduced  to  only  a  small  amount,  while 
there  was  some  constant  negative  pressure.  Usually  the  katheter  could 
not  be  pushed,  under  these  circumstances,  much  deeper.  When  the 
katheter  was  now  retracted,  step  by  step,  it  was  found  that  in  the 
entire  mediastinum,  even  within  the  first  ribs,  such  an  inspiratory  and 
expiratory  negative  pressure  prevailed  as  was  found  in  the  4th 
section,  i.e.  the  highest  attainable  amount  in  the  rabbit  just  experi- 
mented upon,  a  state  which  continued  now  to  remain  the  same  even  at 
every  new  pushing  down,  as  long  as  the  katheter  was  not  entirely  taken 
out.  In  this  latter  case,  if  one  waited  for  some  time  before  intro- 
ducing it  anew,  there  appeared  to  be  at  the  reintroduction  again  some 
differences,  but  they  were  neither  so  pronounced,  nor  so  constant  as 
they  appeared  at  the  first  introduction  of  the  katheter  in  the  medias- 
tinum.    In  some  of  the  cases  in  which  there  was  a  third  section,  i.e.  a 


INTRATHORACIC  PRESSURE. 


225 


total  disappearance  of  the  inspiratory  undulations  before  their  final 
increase,  this  state  seemed  to  remain  in  the  same  locality  even  at  the 
retractions  or  reintroductions  ;  when  the  katheter  Avas  passing  this  place 
at  any  time  or  in  any  direction,  the  inspiratory  undulations  used  to 
disappear.  It  is  worth  while  to  mention  the  fact  that  deep  inspirations, 
e.g.  those  caused  by  dyspnof'a,  were  often  accompanied  by  transient  strong 
undulations  even  in  the  upper  pai't  of  the  mediastinum. 

The  following  few  tables  will  sufficiently  illustrate  the  preceding 
descriptions. 

The  numbers  in  the  first  column  under  the  heading  of  distance 
mean  the  distance  from  the  crico-thyroideal  ligament,  the  unit  being 
5  millimeters:  thus  for  instance  10  means  50  millimeters  from  the  liga- 
ment. The  2nd  and  3rd  columns  indicate  the  absolute  pressure  in  milli- 
meters of  water  at  each  corresponding  step  at  the  inspiration  or  expira- 
tion, —  or  -I-  indicate  if  the  pressure  was  negative  or  positive.  In  the 
4th  column  the  difference  of  the  amount  of  the  inspiratory  increase  of 
the  pressure  is  given.  In  a  5th  column  (when  given)  are  the  notes 
from  the  autopsy  showing  the  corresponding  place  in  the  mediastinum ; 
the  abbreviations  being : — n.  m,  =  no  motion  ;  s.  m.  =  small  motion  ; 
v,  s.  m.  =  very  small  motion  ;  n.  n.  p.  =  no  negative  pressure  ;  int.  =  pleura 
intact,  the  lungs  not  collapsed. 


Experiment  1. 

Large  rabbit,  2800  gram. ;  katlioter  No.  G,  pushed  in  at  once  to  10 
(50  mm.  distance  from  ligament),  progressing  in  steps  of  4  units  (20  mm.). 
Number  of  respirations  36. 


Distance. 

Inspir. 
-    18  mm. 

Expir. 
-  16  nun. 

Diff.  • 

10 

2  nun. 

14 

-    23    „ 

-19    „ 

4    „ 

18 

-    71     „ 

60    „ 

11    „ 

22 

-    92    „ 

-72    „ 

20    „ 

26 

-116    „ 

-70    „ 

46    „ 

30 

-120    „ 

-65    „ 

55    „ 

15—2 


226 


8.   J.   MELTZER. 


Experiment  III. 

Rabbit,  1800  gram.  ;  katheter  No.  5,  at  once  to  10,  .seemed  to  correspond 
to  2nd  rib  ;  respiration  46  p.m. 


Distance. 

Inspir. 

Expir. 

Diff. 

10 

-  14  mm. 

-    6  mm. 

8  mm. 

14 

-32     „ 

-28    „ 

4    „ 

18 

-36    „ 

-20    „ 

16    „ 

22 

-40    „ 

-18    „ 

22    „ 

26 

-46    „ 

-24 

22 

30 

-32    „ 

-28    „ 

4    „ 

26 

-40    „ 

-14    „ 

26    „ 

22 

-40    „ 

-14    „ 

26    „ 

18 

-41    „ 

-20    „ 

21    „ 

14 

-32    „ 

-12    „ 

20    „ 

10 

-32    „ 

-13    „ 

19    „ 

Experiment  V. 
Rabbit,    1350    gram.;    katheter  No.   5,   pushed  to  6  (30mm. 
between  steps,  2  units  (10  mm.).     Respiration  36  p.m. 


distance 


Distance. 

Inspir. 

Expir. 

Diff. 

6 

n.m. 

n.n.p. 

0 

8 

-    4  mm. 

-  2  mm. 

2  mm. 

10 

-    4    „ 

-  2 

2 

12 

-    4    „ 

0 

2 

14 

-    4    „ 

-  2    „ 

2 

16 

-33    „ 

-10    „ 

23    „ 

18 

-32    „ 

-  8    „ 

24    „ 

20 

-32    „ 

-  8    „ 

24    „ 

22 

s.m. 

15    „ 

0    „ 

14 

-30    „ 

-  9    „ 

21    „ 

10 

-28    „ 

-10    „ 

18    „ 

Experiment  VIII. 

Young  rabbit,  1150  gram.  ;  katheter  No.  5,  pushed  to  6  (30  mm.),  both 
pleurae  intact  during  experiment ;  respiration  45  p.m. 
Autopsy;  katheter  in  the  right  side. 


Distance. 

Inspir. 

Expir. 

Diff. 

Locality 
in  mediastinum. 

6 

v.s.m. 

n.n.p. 

0 

above  aperture 

8 

s.m. 

n.n.p. 

0 

1st  rib 

10 

s.m. 

n.n.p. 

0 

1st  intercost.  space 

12 

-    3  mm. 

+  2  mm. 

5  mm. 

14 
16 

18 

-18    „ 
-24    „ 

-28    „ 

-5    „ 
-4    „ 
-6    „ 

13    „ 
20    „ 
22    „ 

20 

-28    „ 

-6    „ 

22    „ 

INTRA  THORA  CIC  PRESS  URE. 


227 


Experiment  X. 

Rabbit,   1700   gram.;    katheter   No.   6;    both  pleurae  visible   and  intact 
during  experiment;  resp.  64  p.m. 

Autopsy;  katheter  found  in  left  side  of  mediastinum  posterior. 


Distance. 

Inspir. 

Expir. 

Diff. 

10 

n.ni. 

u.n.p. 

0 

12 

-  10  mm. 

-     8  mm. 

2  mm. 

14 

n.m. 

-    8    „ 

0 

16 

-     7  mm. 

_     2 

5  mm. 

18 

s.m. 

u.n.p. 

0 

20 

.s.ra. 

n.n.p. 

0 

slight  obstacle  overcome. 

-  20  mm.  15  mm. 
-23  „  15  „ 
-22  „  :  16  „ 
-20  „  !  18  „ 
-28  „  0  „ 
-20  „  18  „ 
-20  „  18  „ 
-23  „  13  „ 
-20  „  18  „ 
-20  „  1  18  „ 
-20  „  18  „ 

-  15  „  1   19  „ 

-  15  '   20 
-10  „  1   25  „ 

-  9  „  !  26  „ 
-10  „  25  „ 
-13  „  22  „ 
-15  „  20  „ 
-12  „  20  „ 
-18  „  20  „ 

-  10  „  20  „ 

-  8  „  ,   20  „ 

-  8  „  I  20  „ 
-15  „  10  „ 

-  15  „  I    0  „ 


22 

-  35  mm 

24 

-38    „ 

26 

-38    „ 

28 

-38    „ 

30 

s.m. 

28 

-  38  mm 

26 

-38   „ 

24 

-36    „ 

22 

-38    „ 

20 

-38    „ 

18 

-38    „ 

16 

-34    „ 

14 

-35    „ 

12 

-35    „ 

10 

-35   „ 

12 

-35    „ 

14 

-35    „ 

16 

-35    „ 

18 

-32    „ 

20 

-38   „ 

22 

-30    „ 

24 

-28   „ 

26 

-28    „ 

28 

-25    „ 

30 

v.H.m. 

Locality 
in  mediastinum. 


1st  rib 

1st  intercost.  space 

2nd  ril) 

3rd  rib 

4th  rib 


228 


8.   J.   MELTZER. 


Experiment  XTII. 

Young  rabbit,   1300  gram.;   katheter  No.    5,   pleura  intact,  no  obstacle 
in  pushing;  resp.  40,  a  little  active. 

Autopsy ;  katheter  in  left  side  of  mediastinum  posterior. 


Distance. 

Inspir. 

Expir. 

Diff. 

Locality 
in  mediastinum. 

8 

n.m. 

n.n.p. 

0  mm. 

1st  rib 

10 

-    5  mm. 

0 

5    „ 

1st  intercost.  space 

11 
12 
13 
14 

-  7    „ 

-  7    „ 

-  7    „ 

-  7    „ 

+  1  mm. 
+  1    „ 
-^1    „ 
+  1    „ 

8    „ 

upper  part  of  2nd  rib 
3rd  rib 

15 
16 
17 

-    9    „ 

-11     „ 

v.s.m. 

+  1    „ 

+  1     „ 

0 

10    „ 

12    „ 

0    „ 

18 

v.s.m. 

0 

0    „ 

5  th  intercost.  space 

19 

-  30  mm. 

-  3  mm. 

27    „ 

20 

-25    „ 

_  2 

23    „ 

21 

22 

-15    „ 
v.s.m. 

-3    „ 
0 

12    „ 
0    „ 

20 

-  23  mm. 

-  3  mm. 

20    „ 

18 
16 

-30    „ 
v.s.m. 

+  1    „ 
0 

31    „ 
0    „ 

14 
12 
10 

-28    „ 
-25    „ 
-25    „ 

+  1    „ 
+  1    „ 
+  1    „ 

29    „ 
26    „ 

26    „ 

Experiment  XV. 
Rabbit,  2500  gram.;  pleura  intact;  resp.  54;  katheter  No.  5  ;  no  autopsy. 


Distance. 

Inspir. 

Expir. 

Diff. 

10 

S.Ul. 

0 

0 

12 

s.m. 

0 

0 

14 

-  16  mm. 

-    8  mm. 

8  mm. 

16 

-15    „ 

-    3     „ 

12    „ 

18 

-16    „ 

-    9    „ 

7    „ 

20 

-12    „ 

0    „ 

12    „ 

22 

-46    „ 

-  19    „ 

27    „ 

24 

-49    „ 

-  14    „ 

35    „ 

26 

-37    „ 

-  10    „ 

27    „ 

28 

-37    „ 

-  10    „ 

27    „ 

26 

-30    „ 

-    4    „ 

26    „ 

24 

-30    „ 

-    4    „ 

26    „ 

22 

-30    „ 

-    3    „ 

27    „ 

20 

-  30    „ 

-    4    „ 

26    „ 

18 

-34    „ 

-    4    „ 

30    „ 

16 

-34    „ 

-  10    „ 

24    „ 

14 

-30    „ 

-  10    „ 

20    „ 

12 

-35    „ 

-10    „ 

25    „ 

INTRATHORACIC  PRESSURE. 


229 


Experiment  XXV. 

Rabbit,  2200  gram. ;  pleura  intact ;  respir.  60,  active ;  suspicion  that  the 
katheter  is  not  air-tight  in  the  mediastinum  ;  paraffine  applied  to  the  wound 
a  few  times. 


Paraffine 


Distance. 

luspir. 

Expir, 

Diff. 

8 

s.m. 

0 

_ 

9 

-     6  mm. 

+  3  mm. 

9  mm. 

10 

-    3    „                +2    „ 
Paraffine 

5    „ 

10 

-    8    „         i       +'i    „ 

12    „ 

13 

-    8    „         '       +3    „ 

11     „ 

15 

-    -2    „         i       +1    „ 
Paraffine 

3    „ 

15 

~    -2    „                 +1     „ 

3    „ 

17 

-40    „         i       +6    „ 

46    „ 

19 

-40    „ 

+  6     „ 

46    „ 

19 


42 


44 


Neglecting  tor  the  present  the  minor  points,  we  may  say  in  short, 
that  according  to  our  experiments,  the  main  inspiratory  undulations 
were  found  to  appear  in  the  mediastinum  posterior  only  below  the  4th 
and  oth  ribs,  while  above  this  the  change  of  the  pressure  during  the 
inspiration  was  either  hardly  measurable,  or  it  did  not  amount  to  more 
than  a  few  millimeters  of  water.  The  result  being  a  surprise  to  me,  I 
distrusted  it  from  the  beginning,  the  more  so  since  in  some  cases  a 
certain  obstacle  had  to  be  overcome  just  before  the  larger  undulations 
put  in  an  appearance.     (See  table  X.  at  20  distance.) 

I  suspected  that  this  sudden  change  might  be  connected  in  some  way 
with  a  perforation  of  the  mediastinal  pleura,  producing  a  certain  degree 
of  collap.se  of  the  corresponding  lung.  I  therefore  took  the  precaution 
to  lay  bare  botb  pleurae  and  to  control  by  this  means  the  condition  of 
the  lungs.  In  young  rabbits  this  is  an  easy  task,  as  it  requires  only  to 
bisect  the  large  muscles  of  the  chest-wall ;  the  entire  lung  and  its 
movements  then  present  themselves  through  the  transparent  pleura 
thoracica,  in  a  distinct  and  instructive  manner.  Indeed,  it  seemed  to 
me  to  be  an  appr(»priatc  method  for  the  demonstration  of  the  motion  of 
the  lungs.  If  there  is  nowhere  any  mention  of  this  method,  I  wish  to 
direct  herewith  attention  to  it.     In  older  rabbits  I  removed  carefully 


230  8.   J.  MELTZER. 

the  intercostal  muscles  in  the  6th  and  7th  intercostal  spaces,  so  as  to 
be  able  to  observe  the  position  of  the  margin  of  the  lungs.  By  this 
means  I  convinced  myself  that  in  no  case  was  there  the  slightest 
retraction  of  the  lung  in  connection  with  the  sudden  change  in  the 
inspiratory  undulations.  In  fact,  there  was  no  degree  of  collapse  in  any 
case  during  the  first  introduction  of  the  katheter.  But  after  many 
retractions  and  reintroductions,  the  lung  corresponding  to  the  side  in 
which  the  katheter  was  located,  showed  indeed  in  a  few  rabbits  a 
tendency  to  collapse. 

This  fact  demonstrates  that  the  pleural  cavity  did  not  remain  intact 
and  that  after  many  reintroductions  air  found  access  to  it.  To  gain  an 
insight  as  to  the  condition  of  the  pleura  in  the  other  cases,  I  discon- 
nected, after  finishing  the  experiment,  the  katheter  from  the  manometer, 
and  allowed  in  this  way  the  atmospheric  air  to  enter  the  mediastinum 
directly.  In  the  majority  of  the  cases  even  then,  the  lung  did  not 
collapse,  a  sure  proof  that  the  pleura  mediastinalis  remained  intact. 
In  some  other  cases  the  lung  did  collapse,  the  mediastinal  pleura, 
accordinglj'^,  had  been  severed  indeed,  but  as  the  lung  did  not  collapse 
before  the  disconnecting  of  the  katheter,  we  may  with  safety  conclude 
that  in  these  cases  no  atmospheric  air  found  access  to  the  mediastinum 
beside  the  katheter ;  in  other  words,  that  at  least  in  these  cases  the 
mediastinum  remained  air-tight  while  the  katheter  was  introduced  into 
it.  As  the  revealed  difference  between  the  upper  and  the  lower  part 
of  the  mediastinum  was  observed  (without  exception)  in  all  the  cases 
studied,  we  may  justly  conclude  that  the  discovered  difference  is 
neither  a  result  of  the  laceration  of  the  pleura  mediastinalis,  nor  is  it 
connected  with  the  entrance  of  more  or  less  atmospheric  air  into  the 
mediastinum  beside  the  katheter.  With  the  last-mentioned  point  I 
shall  deal  more  extensively. 

The  results  obtained  were  in  their  extent  not  only  unexpected,  but 
were  even  in  direct  contradiction  with  my  own  experience  in  testing  the 
intrathoracic  pressure  in  the  oesophagus. 

The  negative  inspiratory  undulations  were  found  in  this  locality, 
at  the  very  entrance  of  the  mediastinum,  to  be  of  a  considerably 
larger  amount  than  was  observed  in  the  entire  upper  third  of  the 
mediastinum  itself.  And  if  we  had  objections  against  the  oesophagus 
on  account  of  the  thickness  of  its  wall  and  the  effects  of  the  muscular 
tissue,  they  were  made  on  the  supposition,  that  the  amount  of  the 
negative  pressure  in  the  oesophagus  falls  short  of  the  real  pressure 
in   the   mediastinum.      The   natural   suspicion   that   I   myself  enter- 


INTRATHORACIC  PRESSURE.  231 

tained  and  which  would  certainly  be  entertained  by  others,  was  that 
the  results  I  arrived  at  are  only  of  an  artificial  nature,  produced  by 
the  faulty  method  I  employed,  the  fault  being  that  the  katheter  was 
not  air-tight  enough  in  the  mediastinum,  that  probably  air  could  get  in 
the  mediastinum  alongside  of  the  katheter,  but  that  the  entrance  of  the 
air  becomes  more  scanty  the  deeper  the  katheter  is  pushed  in,  and 
thence  the  ditference  of  the  negative  pressure  between  the  upper  and 
the  lower  parts.  I  paid  special  attention  to  this  possible  objection,  and 
I  am  now  going  to  show  the  untenability  of  it. 

First  of  all,  it  should  be  remembered,  that  the  present  investigation 
was  not  started  to  ascertain  the  exact  amount  of  the  intrathoracic 
pressure,  the  object  was  merely  the  comparison  of  the  amounts  as  they 
present  themselves  in  different  localities  of  the  thorax. 

JSow,  finding  for  instance,  that  while  the  inspiratory  pressure  in 
deeper  parts  of  the  mediastinum  amounted  to  30  millimeters  water,  in 
the  upper  part  the  pressure  amounted  almost  to  nothing  or  did  not 
exceed  4  or  5  millimeters,  we  may  admit  that  these  are  not  the  real 
amounts,  that  the  real  amounts  have  been  reduced  somewhat  by  the 
invasion  of  atmospheric  air ;  but  if  we  should  go  further  to  explain  the 
entire  difference  between  the  upper  and  the  lower  parts  only  by  the 
interference  of  atmospheric  air,  we  have  then  to  assume  that  the 
facility  for  the  entrance  of  air  beside  the  katheter  is  in  the  upper  part 
of  the  mediastinum  at  least  0  times  greater  than  for  the  entrance  through 
it,  since  the  amount  in  the  upper  part  is  at  the  utmost  ^  of  the  amount 
in  the  lower  part;  an  assumption  which  is,  as  it  seems  to  me,  a  i^^'wri 
improbable.  The  katheter  is  in  the  neck  behind  the  cesophagus  in 
close  connection  with  the  surrounding  tissue,  there  is  no  natural 
channel  leading  to  the  mediastinum,  the  katheter  has  to  bore  its  way 
thither ;  it  is  then  not  likely  that  the  imaginary  space  around  the 
katheter  should  be  a  better  means  tor  the  communication  with  the 
outside  air  than  the  free  lumen  through  the  katheter.  Then  the  con- 
ditions were  not  changed  in  the  upper  part  even  if  a  katheter  with  a 
wider  lumen  was  employeil,  which  could  not  be  the  case  if  the  entire 
effect  depended  upon  the  rivalry  between  the  lumen  of  the  katheter 
and  the  .space  anjiiml  it.  To  make  this  latter  more  impermeable  for 
air  in  many  cases  betore  pushing  the  katheter  down  the  nock  and 
after  iti.scrting  a  cannula  in  the  trachea,  I  have  dressed  the  entire  wound 
with  a  tightly  fitting  bandage  surrounding  the  neck,  an  I  this  jne.ssing 
the  tissue  closjr  to  the  katheter.  Th(3  rosults  have  biM'ii  just  the  same 
as   they  were   found  to  be  without  this  precaution.     And   the    results 


232  S.  J.   MELTZER. 

remained  practically  the  same  after  employing  a  still  safer  method  for 
occluding  the  wound  and  thus  excluding  the  atmospheric  air. 

By  filling  out  the  entire  wound  carefully  with  melted  paraffine,  any 
side  entrance  to  the  mediastinum  is  safely  closed  up.  I  tested  it  by 
artificially  increasing  the  negative  pressure  to  a  higher  amount ;  it 
remained  unaltered  so  long  as  the  paraffine  cover  remained  unbroken. 
Although  this  happens  indeed  when  the  katheter  is  moved,  the 
method  is  perfectly  reliable  if  applied  after  the  katheter  is  at  rest;  and 
this  is  sufficient  for  our  purpose,  since  we  can  occlude  every  time  anew 
before  testing  the  pressure.  No  matter  how  much  air  entered  before- 
hand, after  safe  occlusion  the  inspiratory  change  ought  to  be  in  all 
parts  of  equal  amount,  that  is,  if  the  invasion  of  the  atmospheric 
air  is  at  the  bottom  of  the  manifold  mentioned  differences.  As  we 
just  stated,  the  difference  was  not  affected  by  the  occlusion  (see  Exp. 
XXV.),  and  consequently  it  cannot  be  simply  the  result  of  a  more 
convenient  invasion  of  air  through  a  side  opening  in  the  upper  part  of 
the  mediastinum. 

Aside  from  those  experimental  proofs,  there  is  a  fact  in  the  results 
themselves,  which  speaks  decidedly  against  the  supposition,  that  it  is 
the  access  of  atmospheric  air  by  the  side-ways,  which  cuts  down  the 
negative  pressure  in  the  upper  part  of  the  mediastinum.  It  is  the  fact 
that  at  the  retraction  or  reintroduction  of  the  katheter  the  difference 
disappears  ;  there  is  then  in  the  upper  part  the  same  high  amount  of 
negative  pressure  at  each  inspiration  as  is  foimd  to  be  in  the  lower 
part  of  the  mediastinum.  And  we  can  certainly  not  presume  that  the 
side-ways  became  narrower  by  the  retractions  or  reintrod notions. 

After  all  this,  there  can  hardly  be  any  doubt  that  the  smallness  of 
the  amount  of  the  negative  pressure,  which  was  found  to  take  place  in 
the  upper  part  of  the  mediastinum  during  an  inspiration,  is  not  an 
artificial  phenomenon,  produced  by  some  defect  in  the  experiments,  but 
shews  that  it  is  a  fact  indeed,  that  the  change  in  the  intrathoracic 
pressure  which  prevails  during  an  inspiration,  affects  but  little  the  upper 
part  of  the  mediastinum  ! 

While  thus  defending  the  entire  usefulness  of  the  method  employed, 
so  far  as  concerns  the  main  object  of  this  investigation,  I  am  willing  to 
admit,  that  unless  a  safe  method  is  found  by  which  it  would  be  possible 
to  exclude  positively  any  entrance  of  air  beside  the  katheter,  while  this 
is  pushed  into  the  mediastinum,  the  other  points  of  the  results  obtained 
by  this  method  are  open  to  criticism.  The  amounts  of  the  negative 
pressure  at  the  inspirations  as  well  as  at  the  expirations,  as  they  were 


tNTRATHORACIG  PRESSURE.  233 

obtained  in  the  mediastinum,  iiave  no  claim  on  absolute  correctness; 
they  may  be  indeed  inHuenceil  by  the  entrance  u{  some  air  alongside  of 
the  katheter.  Moreover  these  amounts  vary  with  the  frequency  of 
the  respiration,  with  the  diameter  of  the  lumen  of  the  katheter,  with 
the  length  of  tlie  tube  connecting  the  katheter  with  the  manometer, 
and  perhaps  with  the  side,  on  which  the  katheter  was  introduced,  as  the 
amounts  from  the  left  side  seemed  to  be  smaller  than  those  from  the 
right  side !  Concerning  the  negative  pressure  during  the  expiration, 
we  should  remember  that  in  rabbits,  according  to  Traube  and 
I.  Rosenthal,  the  external  oblicjue  muscles  do  contract  in  normal 
expirations,  which  would  make  the  amount  of  the  negative  pressure 
in  living  rabbits,  smaller  than  that  given  by  Bonders  or  Heynsius, 
who  experimented  on  dead  animals. 

All  these  points  have  not  received  sutiicient  consideration  in  my 
experiments,  as  I  was  mainly  interested  in  the  comparison  of  the 
results  of  the  different  sections  of  the  mediastinum,  obtained  under  the 
same  conditions.  With  somewhat  more  confidence  could  be  regarded 
the  result  showing  a  constant  difference  in  the  amount  of  negative 
pressure  in  the  different  sections  of  the  mediastinum  during  the 
expirations  also.  Though  I  shall  not  discuss  at  length  this  point,  I 
wish  to  say  that  if  we  should  even  admit  that  air  finds  access  to 
the  mediastinum,  and  that  the  invaded  air  affects  the  expiratory 
pressure  in  the  upper  part  of  the  mediastinum  somewhat  more  than  in 
the  lower  part,  it  is  pretty  certain  that  this  is  not  the  only  cause  of  the 
comparatively  pronounced  difference  in  the  amount  of  the  expiratory 
pressure,  the  difference  being  nearly  as  constant  and  as  pronounced  as 
was  the  case  in  the  inspiratory  undulations  ! 

From  the  very  fact  that  there  is  a  difference  between  the  upper 
part  and  the  rest  of  the  mediastinum  in  respect  to  the  intrathoracic 
pressure,  it  follows  that,  no  matter  what  the  cause  of  the  difference  may 
be,  the  mediastinum  does  not  represent  normally  a  connected  cavity  ; 
if  the  cavity  were  so  connected,  there  could  not  be  any  ditference  in 
its  localities  in  respect  to  the  prevailing  pressure,  since  in  a  connected 
cavity  the  pressure  is  the  same  in  all  parts.  It  is  rather  to  be  supposed 
that  the  mediastinal  walls  in  some  way  or  other  a<lliere  together  to 
such  a  degree,  that  one  part  can  not  be  influenced  by  the  pressure 
prevailing  in  another  part.  We  can  now  easily  understand  why  the 
mentioned  difference  was  only  present  at  the  first  introduction,  and  not 
any  more  at  the  retractions  (jr  reintrodiictions;  because  the  first 
introduction  of  the  katheter  transforms  the  mediastinum  into  a  well- 


234  S.   J.   MELTZER. 

connected  channel,  where  the  pressure  can  not  be  otherwise  than  equal 
in  all  its  parts.  And  as  the  oesophagus  is  naturally  such  a  well- 
connected  channel,  we  see  now  further  why  we  found  the  same  pressure 
in  all  its  parts,  and  conceive  a  natural  explanation  for  the  apparently 
singular  fact,  that  the  respiratory  changes  of  the  pressure  should  be 
larger  in  the  upper  part  of  the  thick-coated  oesophagus,  than  in  the 
upper  part  of  the  mediastinum :  it  is  not  the  respiratory  undulations 
in  the  upper  parts  of  the  lungs  directly  transmitted  to  the  upper  part 
of  the  oesophagus  which  we  measure  there,  it  is  only  the  propagated 
pressure  of  its  lower  part  transmitted  there  from  the  lower  parts  of  the 
lungs. 

The  avowed  purpose  of  the  present  investigation,  was  to  infer 
the  amount  of  the  respiration  in  different  localities  from  the  con- 
dition of  the  changes  in  the  intrathoracic  pressure  accompanying 
the  respirations  in  the  corresponding  localities.  Now  as  we  found 
indeed  that  the  changes  of  the  respiration  are  very  little  marked  in 
the  upper  third  of  the  mediastinum,  we  should  proceed  to  conclude 
that  the  respiration  is  considerably  diminished  not  only  in  the  apices  of 
the  lungs,  but  even  in  the  entire  upper  third  at  least  of  the  back  parts 
of  the  lungs.  The  conclusion  means  in  particular  that  the  pressure  in 
the  mediastinum  differs  not  at  all  or  very  little  from  the  pressure  in 
the  pleural  cavity,  and  that  the  pressure  here  may  be  taken  as  an 
exact  expression  of  the  degree  of  breathing  taking  place  within 
the  corresponding  parts  of  the  lungs. 

The  assumption  that  in  some  part  of  the  pleural  cavity  there  may 
prevail  a  pressure  different  from  that  present  in  other  parts,  implies 
further  the  supposition  that  the  pleura  visceralis  adheres  to  the  pleura 
parietalis  so  much  as  to  prevent  the  highest  pressure,  prevailing  in  some 
place  of  the  cavity,  from  being  propagated  over  the  whole  pleural  cavity. 
As  there  are  no  such  anatomical  connections  between  the  two  pleurge  to 
establish  an  adherence,  we  shall  have  to  look  for  "adhesion"  in  the 
physical  sense  to  fill  that  office.  Indeed  it  has  been  claimed  by  some 
authors  that  the  "adhesion"  even  assists  in  overcoming  the  elasticity  of 
the  lungs.  As  the  back  part  of  the  upper  third  of  the  lungs  is  just 
the  part  of  the  lungs  which  is  less  subject  to  the  respiratory  move- 
ments than  any  other  part  of  the  lungs,  we  may  bring  this  point 
into  causal  connection  with  the  assumption,  that  the  same  part  takes 
the  least  share  in  the  act  of  breathing,  i.e.,  the  alveoli  of  this  part 
expand  very  little  during  the  normal  inspiration.  We  may  assume 
further  that  the  upper  parts  of  the  lungs  are  in  the  expiratory  state  in 


INTRATHORACIC  PRESSURE.  235 

a  less  expanded  condition  and  are  better  conformed  to  their  corre- 
sponding part  of  the  thorax  than  the  rest  of  the  lungs  and  therefore 
there  is  none  or  only  little  negative  pressure  in  the  upper  part  of 
the  thorax,  while  it  is  at  rest  in  expiration.  Indeed  there  would 
be  altogether  no  difficulty  in  explaining  why  the  upper  part  of  the 
lungs  should  show  certain  exceptions,  if  only  the  fact  could  be  sure, 
that  the  conditions  I  observed  in  the  mediastinum  have  exactly  the 
same  bearing  upon  the  pleural  cavity  and  upon  the  lungs.  But  having 
been  successful  in  the  research,  I  hesitate  now  to  draw  from  the 
discovered  facts,  those  conclusions  for  which  I  undertook  the  entire 
investigation.  It  seems  now  to  me  that  the  facts  permit  also  the 
theory,  that  the  diminished  negative  pressure  which  was  observed 
in  the  upper  part  of  the  mediastinum  is  restricted  to  its  locality  alone 
and  has  no  bearing  on  the  pleural  jcavity.  The  upper  part  of  the 
mediastinum  harbours  the  aorta,  both  vena?  cavse,  the  trachea,  and 
the  bronchi,  all  of  them  are  connected  among  themselves  and  with 
the  oesophagus  by  connective  tis.sue.  The  katheter  is  in  this 
vicinity  separated  from  the  pleural  cavity  not  only  by  the  thin  medi- 
astinal pleura,  but  by  a  pi'etty  thick  wall  formed  by  all  the  tubes 
mentioned  above,  while  in  the  lower  part  of  the  mediastinum  there 
is  indeed  nothing  else  to  separate  the  katheter  from  the  pleural  cavity 
than  the  thin  mediastinal  pleura.  The  appearance  of  the  mediastinum 
intensifies  the  supposition  that  there  exists  indeed  a  certain  anatomical 
difference  between  the  upper  and  the  lower  part  of  the  mediastinum. 
The  slight  obstacle  which  was  often  met  just  before  reaching  that 
portion  at  which  the  strong  inspiratory  undulations  put  in  an  appear- 
ance, may  come  from  some  stouter  structure  of  the  connective  tissue, 
located  at  this  boundary  line,  and  which  may  help  at  the  same  time  to 
prevent  the  propagation  of  the  pressure  from  the  lower  to  the  upper 
part  of  the  mediastinum.  The  only  objection  that  could  be  made 
against  this  theory  is,  that  according  to  it,  that  part  in  the  upper  third 
which  is  least  .separated  from  the  pleural  cavity  should  show  stronger 
undulations;  but  in  the  region  next  to  the  apex  of  the  lungs  is 
contained  the  least  amount  of  thoracic  viscera,  and  just  here  were 
hardly  any  inspiratory  undulations  to  be  noticed.  There  is  not  such  an 
importance,  however,  in  this  <jbjection  as  to  be  sufficient  to  exclude  the 
po.ssibility  of  this  hypothesi.s.  I  mean  to  say  this: — although  it  seems 
to  me  that  my  experiments  on  the  mediastinum  make  it  indeed 
probable  that  the  apices  and  the  back  part  of  the  upper  third  of 
the  lungs  do  not  participate  in  the  breathing  so  largely  as  the  other 


236  S.  J.   MELTZER. 

parts  of  the  lungs  do,  in  consideration  of  the  importance  of  this 
conclusion,  we  should  not  consider  it  as  proven,  until  it  has  been  tested 
by  experiments  made  on  the  pleui'al  cavity,  directly  or  within  the  lungs 
themselves. 

Besides  the  relations  to  the  breathing  of  the  upper  parts  of  the 
lungs,  the  condition  discovered  to  prevail  in  the  upper  part  of  the 
mediastinum  has  an  important  bearing  on  the  question  of  the  origin  of 
the  respiratory  undulations  of  the  blood-pressure.  Without  entering  into 
details  of  the  very  complex  theme,  it  is  sufficient  to  say,  that  with 
exception  of  a  very  few  all  the  writers  on  this  subject  agree  with  the 
view  set  forward  and  developed  by  Ludwig,  Bonders  and  Einbrod, 
that  the  increase  and  the  decrease  of  the  intrathoracic  negative 
pressure  accompanying  the  respirations,  have  a  great  deal  to  do  with 
the  undulations  of  the  blood-pressure.  During  the  inspiration  both 
venae  cavaa  and  the  right  auricle  are,  so  it  is  generally  assumed,  under  a 
considerably  lower  pressure  than  the  veins  outside  of  the  thorax,  which 
difference  of  pressure  causes  greater  inrush  of  blood  into  the  great 
thoracic  veins  and  the  right  auricle,  and  thus  more  blood  comes  into 
the  ventricle  etc.;  the  expiration  on  the  other  hand  by  the  diminished 
intrathoracic  negative  pressure  diminishes  the  influx  of  blood  into  the 
ventricle.  The  same  conditions  have,  so  it  is  calculated,  an  opposite 
but  a  smaller  effect  on  the  aorta.  Now  we  have  seen  in  our  experiments 
that  the  inspiratory  changes  in  the  intrathoracic  pressure  are  very 
small  in  the  upper  part  of  the  mediastinum,  amounting  only  to  a  few 
millimeters  of  water,  the  main  change  in  the  pressure  occurring  in  the 
lower  part  of  the  mediastinum.  As  the  upper  part  reaches  as  far  deep 
as  the  5th  or  6th  rib,  so  this  part  contains  the  entire  superior  vena 
cava,  the  arcus  aortas,  the  auricles,  and  a  considerable  part  of  the 
inferior  vena3  cavai  and  the  descending  aorta.  In  short,  the  main 
circulatory  parts  which  are  expected  to  be  influenced  by  the  consider- 
able change  in  the  intrathoracic  pressure,  are  located  in  that  part 
of  the  mediastinum  where,  according  to  my  experiments,  very  little 
change  occurs.  Thus  my  experiments  seem  to  destroy  nearly  the 
entire  basis,  upon  which  the  prevailing  theory  concerning  the  respiratory 
undulations  of  the  blood  pressure  rests  ! 

I  content  myself  for  the  present  with  this  short  reference  to  the 
subject,  awaiting  firstly  a  confirmation  of  the  facts  I  have  stated  here.  I 
wish  only  to  add  that  ,by  the  method  of  introducing  a  tube  in  the  medi- 
astinum posterior  without  influencing  the  respiration,  it  is  possible  to 
exclude  entirely  the  respiratory  undulations  of  the  intrathoracic  pres- 


INTRATHORACIC  PRESSURE.  237 

sure,  and  it  will  thus  be  possible  to  investigate  directly,  the  share 
those  undulations  of  the  intrathoracic  pressure  have  in  the  undulations 
of  the  blood  pressure. 


EXPLANATION    OF   THE   CURVES. 

The  cnrvps  have  been  obtained  by  connecting  the  katheter  with  a  Marey's 
tanilxiur,  the  lever  of  which  transmitted  the  respiratory  undulations  of  the 
intrathoracic  pressure  on  the  smoked  jmper,  which  covered  the  revolving 
cylinder  of  a  i-ecording  apparatus.  The  negative  pressure  accompanying  the 
inspiration  i"arefies  the  air  in  the  tambour,  and  thus  makes  the  lever  of  the 
tambour  descend;  the  ascension  of  the  lever  corre.sponds  to  the  expiration. 
Below  the  inspiratory  undulations  the  lever  of  a  time-marker  recorded  the 
time  in  seconds.  The  distance  between  the  lines  of  the  two  levers,  ti'aced 
l»efore  the  katheter  was  introduced  into  the  chest,  represents  the  condition  of 
the  air  in  the  tambour  under  atmospheric  pressure.  A  smaller  distance 
means  a  negative,  a  greater  di.stance  a  positive  pressure. 

The  Curves  on  Plates  VIII.  A  and  VIII.  7>  are  selected  fi'om  quite  a  great 
number  of  curves,  all  of  which  show  quite  the  same  proj)ortion  between  the 
undulation  of  the  upper  and  lower  parts  of  the  mediastinum,  the  difference 
consisting  only  in  the  absolute  dimensions  of  the  undulations  obtained  from 
the  lower  parts,  a  difference  which  is  even  to  be  seen  in  the  pi-esent  two 
curves.  Even  the  undulations  in  VIII.  J]  are  not  nearly  as  large  as  I  obtained 
in  some  animals.  Each  of  these  curves  represents  an  entire  experiment.  The 
katheter  lias  been  pushed  into  the  chest,  in  these  experiments,  from  6  at  once 
to  10  units,  this  distance  corresponding  in  VIII.  B  to  the  fii'st  ribs,  and  in 
VIII.  A  to  the  fir.st  intercostal  spaces.  The  numbers  on  the  curves  mean  the 
distances  from  the  crico-thyroideal  ligament,  a  unit  being  5  mm.  (10  means 
50  mm.).  After  recording  the  undulation  in  one  position,  the  cylinder  was 
stopped  and  the  katheter  pu.shed  one  unit  deeper;  then  the  cylinder  was  again 
put  in  rotation,  and  so  on  until  the  probable  end-point  of  the  mediastinum 
was  reached;  and  then  the  retraction  followed.  The  position  of  the  tambour 
and  the  time-marker  remained  the  same  during  the  entire  experiment.  The 
direction  of  the  curve  downward  means  inspiration,  and  iq)ward  means 
expiration;  the  marks  above  the  undulations  sliow  the  beginning,  the  numbers 
below,  the  end  of  the  undulations,  corres))onding  to  the  distance  given  in  the 
numl>er.  In  both  of  the.se  exj)eriments  there  has  been  .some  active  expira- 
tion. 

Plate  VIII.  A  is  olitained  from  a  rablnt  ir)00  gram.,  with  a  katheter  No. 
5  ;  lungs  visible  through  pleura;  int.  means  that  the  pleural  cavity  remained 
intact.      In  the  distance  from  10  to  12,  we  see  hardly  perceptible  undulations; 


238  >S'.   /.   MELTZER. 

fi'om  12  to  16  they  are  incT'easing  gradually;  from  16  to  19  tliey  disappear 
again ;  at  1 9  there  is  a  sudden  inci'ease  in  the  inspiratory  undulation,  and 
with  only  a  small  gi'adual  increase  remaining  rather  about  the  same  to  25  ; 
at  27  there  is  again  no  motion,  and  at  26  they  are  irregular,  and  smaller  as  in 
the  preceding  section.  The  level  of  the  expiratory  line  remained  between  10 
and  12  like  it  was  before  the  introduction  of  the  katheter,  from  12  to  19 
there  was  a  very  slight  degree  of  negative  pressure  ;  its  main  increase  occurs 
suddenly  at  19  and  continues  to  be  about  the  same  in  the  remainder  of  the 
mediastinum,  being  even  a  little  more  pronounced  in  the  last  section  (27), 
where  no  more  inspiratory  undulations  are  to  be  seen.  Plate  VIII.  B  is  ob- 
tained from  a  rabbit  of  1800  gram.,  with  a  katheter  No.  5,  the  pleural  cavity 
remaining  intact  even  after  admitting  air  to  the  mediastinum.  We  meet  in 
this  curve  in  the  main  with  the  same  conditions  as  in  VIII.  A^  with  the  differ- 
ence that  the  large  undulations  appear  in  a  deeper  part  of  the  mediastinum  ; 
there  is  a  visible  increase  in  the  inspiratory  undulations  at  the  retraction, 
and  there  is  no  negative  pressure  at  the  expiration,  rather  a  little  positive 
pressure  throughout  the  experiment,  the  contraction  of  the  expiratory  muscles 
being  pronounced. 


JOURN,  PHYSIOLOGY 


VOL,  XIII  PLATEVIII.J 


nf^r^rrnri 


I    I     I 1 I I L, 


Expir. 


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Rabbit 
1500  GroLmm 
Kitheter  N?5 


Insp. 


»»■ 


ntridge  Engraving   Company. 


JOURN.  PHYSIOLOGY 


VOL.XIII.PLATEVIIiy/ 


^J~VM~ 


20 


J I I I I L_J_U I     I      I      I      I 


hh 


25  ml. 


I        I     I I I L 


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26  int. 


I        I     I       I        I I LJ I I I I 1 — I 1 — I L_l 1 I U 


Exp/r. 


Vtt 


Rabbit 
1800  Gra-mm 
Katheter  Wb. 


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Insp. 


»»- 


Cambridge   Engiaving   Company 


^'eltzer  ^ 

On  the  respiratory  changes  in  the   ^^ 
i  n-*  rathoracic  pressure.*. 


